/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.binary;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Provides Base64 encoding and decoding in a streaming fashion (unlimited size). When encoding the default lineLength
 * is 76 characters and the default lineEnding is CRLF, but these can be overridden by using the appropriate
 * constructor.
 * <p>
 * The default behaviour of the Base64OutputStream is to ENCODE, whereas the default behaviour of the Base64InputStream
 * is to DECODE. But this behaviour can be overridden by using a different constructor.
 * </p>
 * <p>
 * This class implements section <cite>6.8. Base64 Content-Transfer-Encoding</cite> from RFC 2045 <cite>Multipurpose
 * Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</cite> by Freed and Borenstein.
 * </p>
 * <p>
 * Since this class operates directly on byte streams, and not character streams, it is hard-coded to only encode/decode
 * character encodings which are compatible with the lower 127 ASCII chart (ISO-8859-1, Windows-1252, UTF-8, etc).
 * </p>
 * 
 * @author Apache Software Foundation
 * @version $Id: Base64OutputStream.java 799806 2009-08-01 04:33:17Z ggregory $
 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>
 * @since 1.4
 */
public class Base64OutputStream extends FilterOutputStream {
private final boolean doEncode;

private final Base64 base64;

private final byte[] singleByte = new byte[1];

/**
 * Creates a Base64OutputStream such that all data written is Base64-encoded to the original provided OutputStream.
 * 
 * @param out
 *OutputStream to wrap.
 */
public Base64OutputStream(OutputStream out) {
this(out, true);
}

/**
 * Creates a Base64OutputStream such that all data written is either Base64-encoded or Base64-decoded to the
 * original provided OutputStream.
 * 
 * @param out
 *OutputStream to wrap.
 * @param doEncode
 *true if we should encode all data written to us, false if we should decode.
 */
public Base64OutputStream(OutputStream out, boolean doEncode) {
super(out);
this.doEncode = doEncode;
this.base64 = new Base64();
}

/**
 * Creates a Base64OutputStream such that all data written is either Base64-encoded or Base64-decoded to the
 * original provided OutputStream.
 * 
 * @param out
 *OutputStream to wrap.
 * @param doEncode
 *true if we should encode all data written to us, false if we should decode.
 * @param lineLength
 *If doEncode is true, each line of encoded data will contain lineLength characters (rounded down to
 *nearest multiple of 4). If lineLength <=0, the encoded data is not divided into lines. If doEncode is
 *false, lineLength is ignored.
 * @param lineSeparator
 *If doEncode is true, each line of encoded data will be terminated with this byte sequence (e.g. \r\n).
 *If lineLength <= 0, the lineSeparator is not used. If doEncode is false lineSeparator is ignored.
 */
public Base64OutputStream(OutputStream out, boolean doEncode, int lineLength, byte[] lineSeparator) {
super(out);
this.doEncode = doEncode;
this.base64 = new Base64(lineLength, lineSeparator);
}

/**
 * Writes the specified <code>byte</code> to this output stream.
 * 
 * @param i
 *source byte
 * @throws java.io.IOException
 * if an I/O error occurs.
 */
public void write(int i) throws IOException {
singleByte[0] = (byte) i;
write(singleByte, 0, 1);
}

/**
 * Writes <code>len</code> bytes from the specified <code>b</code> array starting at <code>offset</code> to this
 * output stream.
 * 
 * @param b
 *source byte array
 * @param offset
 *where to start reading the bytes
 * @param len
 *maximum number of bytes to write
 * 
 * @throws java.io.IOException
 * if an I/O error occurs.
 * @throws NullPointerException
 * if the byte array parameter is null
 * @throws IndexOutOfBoundsException
 * if offset, len or buffer size are invalid
 */
public void write(byte b[], int offset, int len) throws IOException {
if (b == null) {
throw new NullPointerException();
} else if (offset < 0 || len < 0) {
throw new IndexOutOfBoundsException();
} else if (offset > b.length || offset + len > b.length) {
throw new IndexOutOfBoundsException();
} else if (len > 0) {
if (doEncode) {
base64.encode(b, offset, len);
} else {
base64.decode(b, offset, len);
}
flush(false);
}
}

/**
 * Flushes this output stream and forces any buffered output bytes to be written out to the stream. If propogate is
 * true, the wrapped stream will also be flushed.
 * 
 * @param propogate
 *boolean flag to indicate whether the wrapped OutputStream should also be flushed.
 * @throws java.io.IOException
 * if an I/O error occurs.
 */
private void flush(boolean propogate) throws IOException {
int avail = base64.avail();
if (avail > 0) {
byte[] buf = new byte[avail];
int c = base64.readResults(buf, 0, avail);
if (c > 0) {
out.write(buf, 0, c);
}
}
if (propogate) {
out.flush();
}
}

/**
 * Flushes this output stream and forces any buffered output bytes to be written out to the stream.
 * 
 * @throws java.io.IOException
 * if an I/O error occurs.
 */
public void flush() throws IOException {
flush(true);
}

/**
 * Closes this output stream and releases any system resources associated with the stream.
 * 
 * @throws java.io.IOException
 * if an I/O error occurs.
 */
public void close() throws IOException {
// Notify encoder of EOF (-1).
if (doEncode) {
base64.encode(singleByte, 0, -1);
} else {
base64.decode(singleByte, 0, -1);
}
flush();
out.close();
}

}
